Magnetic and half-metallic properties of Cr-doped β-SiC

The Cr doping concentration dependence of the electronic properties including bonding characteristic and spin band gap of SiC dilute magnetic semiconductor is studied by employing first-principles pseudopotential plane-wave method based on density functional theory within generalized gradient approximation. For the cubic β-SiC crystal, the calculated lattice constant is a₀=4.36 Å and the bulk modulus is B₀=208.14 GPa. The 64 and 8-atom supercell models are employed which corresponds to the impurity concentration of 3 and 25%, respectively. In the case of 3% impurity concentration, the Cr atoms substituting for C induces large stress on the neighboring Si atoms due to the significant difference in atomic size. On the other hand, in 25%-doped SiC:Cr, the adjacent Si atoms moved away from the Cr atom. Calculations of the magnetic moment and magnetization energy is done in which the latter is defined as the energy difference between the ferromagnetic phase and paramagnetic phase of SiC:Cr. Results show that the SiC:Cr has permanent magnetic moments of 2μ_B regardless of the substitution site and the studied doping concentration. Also, calculation of density of states is done resulting in the determination of a wide spin band gap of 1.58 eV for the SiC:Cr.